General Motors(WASHINGTON) -- Some U.S. senators Thursday called on General Motors CEO Mary Barra to fire the company’s top lawyer as executives testified on the ongoing investigation into the ignition switch malfunction in some GM vehicles.

Sen. Claire McCaskill, D-Mo., asked Barra why she did not fire Michael Millikin, GM’s corporate counsel, who said he first heard about the problems with the ignition switches this year.

“This is either gross negligence or gross incompetence,” said McCaskill, chairwoman of the Senate Commerce, Science and Transportation’s subcommittee on Consumer Protection, Product Safety, and Insurance.

Barra, who appeared on Capitol Hill for the fourth time this year, defended her decision to not fire Millikin, saying she needed him on her team to help fix the company’s problems and enhance their products’ safety.

“I think there’s been a blind spot here. I really do,” McCaskill said in response. “I think the failure of this legal department is stunning.”

Sen. Richard Blumenthal, D-Conn., said Millikin and his staff “enabled a cover-up, concealment, deceit and even fraud.”

“Lawyers typically are supposed to be the corporate conscience. They’re supposed to be the ones that make sure the corporation complies with the law,” Blumenthal said.

Also testifying Thursday was Kenneth Feinberg, who is responsible for administering the company’s compensation fund. Both Feinberg and Barra said the compensation fund would be uncapped, and victims and families can begin filing claims next month.